Abstract: As scientific evidence documenting the health hazards posed by environmental tobacco smoke (ETS) continues to mount, workplace decision makers have more reason than ever to protect employees from exposure to ETS on the job. The U.S. Environmental Protection Agency concluded in January 1993 that each year ETS kills an estimated 3,000 adult nonsmokers from lung cancer and that the workplace is a significant source of ETS. In a recent study, nonsmoking employees exposed to ETS at work but not at home had significantly higher levels of a nicotine metabolite in their blood than did nonsmoking workers with no work or home exposure to ETS. Levels of exposure to ETS are lowest in smokefree workplaces.